Anatomy, Evolution, and Functional Significance Of
Total Page:16
File Type:pdf, Size:1020Kb
ANATOMY, EVOLUTION, AND FUNCTIONAL SIGNIFICANCE OF CEPHALIC VASCULATURE IN ARCHOSAURIA A dissertation presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Jayc Clinton Sedlmayr June 2002 This dissertation entitled ANATOMY, EVOLUTION, AND FUNCTIONAL SIGNIFICANCE OF CEPHALIC VASCULATURE IN ARCHOSAURIA BY JAYC CLINTON SEDLMAYR has been approved for the Department of Biological Sciences and the College of Arts and Sciences by Lawrence M. Witmer Associate Professor of Anatomy Leslie A. Fleming Dean, College of Arts and Sciences Sedlmayr, Jayc Clinton PhD. June 2002. Biological Sciences Anatomy, Evolution, and Functional Significance of Cephalic Vasculature in Archosauria (398 pp.) Director of Dissertation: Lawrence M. Witmer Cephalic vasculature is an integral component of the vertebrate head, having a major effect on morphological organization, physiological processes, and various mechanical functions (e.g., erectile tissues). It is thus surprising that so little is known about cephalic vasculature in Archosauria, a major amniote clade that today includes crocodilians and birds and in the past included non-avian dinosaurs, pterosaurs, and a variety of basal forms. No comparative studies exist on archosaur head vasculature and no previous attempt has been made to determine homologous structures and patterns across Archosauria. Better understanding of archosaur head vasculature is key to interpreting and reconstructing the evolution of heads and head vasculature in amniotes. This study addresses this problem by documenting and comparing cephalic vascular structures and patterns in the extant archosaur clades Crocodylia (Alligator mississippiensis, Crocodylus spp.) and Aves (Anas platyrhynchos, Struthio) and makes hypotheses of homology based on similarity. Data were attained from a variety of techniques including vascular injection, gross dissection, production of vascular corrosion casts, and the development of a novel stereoangiographic technique. Emphasis is given to the relationships of vessels to other soft-tissue structures and the bony skull, and causal associations between vascular structures and their osteological correlates are identified. These findings are discussed in light of the radical morphological changes that occur in birds (e.g., brain enlargement) and crocodilians (e.g., basicranial metamorphosis) to produce their highly apomorphic head anatomies that considerably deviate from the ancestral condition and were hypothesized to significantly effect and alter head vasculature in extant archosaurs. The striking conclusion of the research is that despite their different cephalic morphologies, the vascular structures and patterns in Aves and Crocodylia are very similar. In several areas these vascular structures had clear osteological correlates shared by the two clades, and that are identifiable in fossil archosaurs. Crocodilians and birds share several, interconnected, potential vascular physiological devices that would allow for brain temperature regulation. This interconnected network may further serve as a transport system for products produced in the Harderian gland and retina to the brain. Approved by Lawrence M. Witmer Associate Professor of Anatomy 5 DEDICATION To my ancestors—for my existence and their genes and their epigenetic influences. Especially Harriet Plattner, Fred and Ilene Sedlmayr whose nurturance, dedication, and skill in rearing is largely responsible for the man who produced this document. For all the trips to natural history museums and zoos, and for all the books and instruction on Life that my family provided and encouraged. To my educators and instructors who whetted and satiated my insatiable curiosity and who provided and facilitated the knowledge required to produce this dissertation. Suzanne Hiltz, Valerie Hinchliff, Dudley Weiland, Bonnie Harden, Joe Domko, Elaine Anderson, James Hanken, Alan De Quieroz, Richard Stuckey, Bryan Small, Audrone Biknevicus, and Lawrence Witmer stand out. To my wife Melissa Sedlmayr for Being. To the memories of Charles Robert Darwin and George Gordon, Lord Byron for perspective, inspiration, and guidance through my dalliances in all things biological. 6 ACKNOWLEDGMENTS Very special thanks to my committee members Audrone Biknevicus (Ohio University), Robert Carr (Ohio University), Stephen M. Reilly (Ohio University), John Wible (Carnegie Museum of Natural History), and Lawrence Witmer (Ohio University). I had great admiration for John Wible’s research long before becoming a graduate student. My early perusals of John’s work deeply inspired my interest, and love, for the blood vascular system and its evolution. John Wible has significantly contributed to our understanding of mammalian blood vasculature, and my original intent upon embarking on this study was to make a similar contribution to our knowledge of archosaurian blood vasculature—although a seemingly impossible task, I can only hope that this dissertation comes close to meeting my goal. It is for all these reason that I am honored to have had John serve on my committee. The original draft of this dissertation presented to John was in parts unseemly, and John’s role as a fount of anatomical knowledge was extended to that of proofreader and editor to which I am forever grateful. Robert Carr contributed a significant amount of time and effort to this manuscript. As one of the more erudite vertebrate anatomists I have had the pleasure to know, Bob has been a constant source of anatomical information and a bewildering array of ideas and insights. Stephen Reilly has been a strong advocate of graduate research during my stay at Ohio University and an enthusiastic supporter of this dissertation. In fact, Steve’s passionate interest in evolutionary morphology was a frequent source of inspiration. Audrone Biknevicus frequently provided me with advice and assistance that was critical in getting me through this process. Audrone further served as 7 one of my gross anatomy instructors, and it was from Audrone that I truly learned head anatomy (in considerable detail). Just as important, Audrone was always available to provide emotional assistance. Finally, to my advisor Lawrence Witmer, who labored intensely on this manuscript and who taught me everything from numerous lab techniques to scientific illustration. Most importantly, Larry taught me how to conduct scientific research. I had the great fortune of apprenticing under one of today’s greatest anatomists. Larry’s perspective on comparative anatomy permeates the entirety of this dissertation. I thank Robert Henry (College of Veterinary Medicine, University of Tennessee) and Kevin Zippel (National Amphibian Conservation Center, Detroit Zoological Society) for initial instruction in vascular injection techniques, and Tim Ganey (Atlanta Medical Center) and Julian Baumel (Burke Museum, Seattle) for sharing their expertise in radiopaque vascular injection media and methods. Joseph Eastman and Audrone Biknevicius (Ohio University) provided access to x-ray facilities. Robert Hikida (Ohio University) provided helpful advice and training in a wide array of anatomical approaches. Scott Moody (Ohio University) provided specimens and helpful discussion. Special thanks to Ruth Elsey and The Rockefeller Wildlife Refuge, Grand Chenier, Louisiana for providing Alligator specimens. Kent Vliet (University of Florida) and the St. Augustine Alligator Farm, St. Augustine, Florida, provided Alligator and Crocodylus specimens. For access to specimens, thanks to: Kevin Padian, Pat Holroyd, and John Hutchinson, University of California Museum of Paleontology, UC Berkeley; Angela Milner, Sandra Chapman, and David Gower, Natural History Museum of London; Rupert Wild, Staatliches Museum für Naturkunde, Stuttgart; Michael Maisch, University of Tübingen; Dino Frey, Staatliches Museum für Naturkunde, Karlsruhe; Johann Welman, National Museum, Bloemfontein, South Africa; Mike Raath and Bruce Rubidge, Bernard 8 Price Institute of Paleontology, Johannesburg; Heidi Fourie, Transvaal Museum, Pretoria; Anusuya Chinsamy-Turan, Derek Ohland, and Sheena Kaal, South African Museum, Cape Town. Clay Corbin (Ohio University) provided invaluable advice on statistical approaches and also reviewed the first chapter. Thanks to Scott Sampson (University of Utah), John Ruben (Oregon State University), Willem Hillenius (College of Charleston), Casey Holliday (Ohio University), Andrew Clifford (Ohio University), Sue Simon (Ohio University), Sue Rehorek (Slippery Rock University of Pennsylvania), Debbie Wharton (Universtity of Bristol), Pat O’ Conner (Ohio University), Bryan Small (Denver Museum of Nature and Science), and Michael Papp for additional productive discussion and assistance. Dana Zurn, Stephanie Strange, and Anne Stewart provided financial support and assistance. Ryan Ridgely (Ohio University), Andrew Lammers (Ohio University), and Melissa Sedlmayr helped with tables and illustration. I could never have completed (or survived) this dissertation without my wife, Melissa. Funding was provided by Ohio University (Departments of Biological Sciences and of Biomedical Sciences), and the National Science Foundation (IBN-9601174 and IBN-0076421). 9 TABLE OF CONTENTS Dedication .............................................................................................................................................5 Acknowledgments................................................................................................................................6